(a) Field of the Invention
The present invention relates to a method for controlling engine torque of a hybrid electric vehicle (HEV).
(b) Background Art
As is generally known in the art, a hybrid electric vehicle (HEV) is a vehicle with a gasoline engine and an electronic throttle control (ETC) device. An electric motor is connected to the ETC. The vehicle charges a battery with energy recovered by the motor.
HEVs are intended to have good fuel efficiency and exhaust performance and, in order to accomplish such an object, it is necessary to minimize consumption of engine power. Methods for minimizing consumption of engine power include a drive control method for driving at an optimum driving point of the engine by a motor assist, an idle-stop control method, and the like.
The motor assists the restart of the engine when releasing the idle-stop state. After the idle-stop state is released, a motor torque is generated, and the engine receives the motor torque to perform an initial injection and ignition, thus generating an engine torque.
An engine RPM and torque thus generated assist an oil pressure generation of a transmission to generate a clutch hydraulic pressure, and the generated clutch hydraulic pressure operates the clutch to transmit power to the wheels.
However, one of the most significant problems of the hybrid electric vehicle at present is a delay in the vehicle start after the release of the idle-stop state. The reason for the delay is the time taken to generate the engine RPM and the time required for generating the oil pressure of the transmission to control the clutch.
Accordingly, a control method of the motor, engine and transmission is necessary in the vehicle start process from the idle-stop state.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art that is already known to a person skilled in the art.